1. Field of the Invention
This invention relates to a recording medium suitably used for the ink jet recording method, particularly to a recording medium having excellent absorptivity and color forming characteristic of an aqueous ink, as well as excellent sharpness of the recorded image obtained.
Further, the present invention relates to a recording medium which can provide a recorded image with little in-room decoloration of the image and excellent storability of the image and a recording method which can provide the above recorded image.
Further, the present invention relates to a recording medium having excellent water resistance and light resistance of the recorded image, while having various characteristics as mentioned above.
2. Related Background Art
In the prior art, as the recording medium for ink jet recording, there have been known:
(1) one obtained by making paper composed mainly of pulp into a sheet with low sizing degree like filter paper or blotting paper;
(2) one having an ink absorbina layer by the use of a porous inorganic pigment provided on a base paper with low ink absorptivity such as usual paper of fine quality, etc., as disclosed in Japanese Laid-open Patent Publication No.56-148585, etc.
On the other hand, in the ink jet recording system for which formation of a color image of high quality and high resolution is particularly demanded, the recording medium to be used is required to have the following characteristics, namely:
(1) good color forming characteristic of the ink attached on the recording medium;
(2) good true sphericity of the ink dot;
(3) good ink absorption capacity such that the ink attached will not flow out even when a plurality of ink droplets may be attached on the same spot;
(4) good ink fixability such that the ink droplets attached will not be blurred even when they may be rubbed immediately after attachment;
(5) good image storability of the image formed such as water resistance, light resistance, etc.
However, no recording medium which satisfies all of the above requisite characteristics has been known yet.
Recently, the particular problem of in-room decoloration of the recorded image inherent in coated paper has been looked at closely.
The problem of light resistance which has been recognized in the prior art is a problem of fading of the image by irradiation of, for example, UV-ray or visible light, etc., on any image printed on any kind of paper from papers for PPC in general or fine quality paper to coated papers for ink jet. However, the problem of in-room decoloration as herein mentioned is a problem separate from light resistance which occurs in the image also stored in, for example, a place where no direct sunlight is irradiated, but does not occur in the image printed on a non-coated paper such as paper for PPC, etc.
For example, the method as disclosed in Japanese Laid-open Patent Publication No. 60-49990 is a method for improving light resistance, and no effect can be seen for in-room decoloration. Thus, the problem of in-room decoloration is a Droblem inherent in coated paper, and it may be estimated to be a problem caused by the pigment forming the coated layer.
For example, the coated paper by use of highly active silica as disclosed in JaDanese Laid-open Patent Publication No. 56-185690 can give an image with high optical density, while it involves a marked problem of in-room decoloration. On the contrary, if fillers in general for paper with low specific surface area such as calcium, kaolin, talc, silica, etc. are used, although in-room decoloration may be suppressed, there is now the problem that the image density is lowered.
Thus, particularly the problems of in-room decoloration and image density are antagonistic to each other, and they have been problems not solved by the prior art technique.